This invention relates to power take-off (PTO) drivelines for use in agricultural and industrial vehicles.
It is well known in, for example, agricultural tractors to provide a PTO driveline at the front or rear of the tractor which includes a wet clutch which when engaged delivers power to a PTO output shaft to drive an implement or attachment at the front or rear of the tractor. Such wet clutches are supplied with cooling/lubricating fluid from a reservoir in order to reduce wear of the clutch and prevent overheating.
The provision of a sufficient flow of cooling/lubricating fluid to such a wet clutch in an economic and efficient manner can cause problems.
It is an object of the present invention to provide an improved form of PTO driveline which is suitable for use in an agricultural tractor and which addresses the above fluid supply problem.
Thus according to the present invention there is provided a vehicle PTO driveline in which a PTO input shaft drives a PTO wet clutch which when engaged drives a PTO output shaft, the driveline having an eccentric formation on the input shaft which oscillates a pumping piston when the input shaft rotates, the oscillating piston pumping cooling/lubricating fluid around a circuit which includes the wet clutch and a fluid reservoir provided by part of a housing which encloses the driveline, characterised in that the piston is connected with the eccentric formation by a ring which surrounds the eccentric formation and a hollow tube which is attached to the ring and which carries the piston at a lower end, the piston oscillating inside a chamber when the input shaft rotates, said chamber being connected with the fluid reservoir and the oscillating piston pumping the fluid along the hollow tube into the ring which then delivers the fluid into internal passages in the input shaft from where the fluid flows to the wet clutch.
The oscillating piston draws the fluid from the reservoir via a non-return valve arrangement.
The wet clutch may be a multi-plate clutch engaged by an end pressure plate which is moved hydraulically or mechanically to engage the clutch and thus drive the PTO output shaft.
The driveline may be arranged so that when the PTO wet clutch is disengaged flow of fluid to the wet clutch is cut-off to reduce drag across the wet clutch.
The wet clutch may be connected with the output shaft via reduction gearing and a free play device may be provided in the drive line on the input side of the reduction gearing which allows limited rotation of the output shaft when the output shaft is stationary.
A driveline in accordance with the present invention is particularly suitable for use as the front PTO driveline of a tractor due to its inherent simplicity and compactness.
The PTO clutch may be connected with the output shaft via reduction gearing and a limited rotational free play device may be provided in the driveline on the input side of the reduction gearing which allows limited manual rotation of the output shaft by a vehicle operator when the output shaft is not driven by the clutch.
In such an arrangement the PTO clutch may include a brake which has a brake disc rotatable with the output shaft and which, when the clutch is not engaged, is held against a braking surface on a housing of the driveline to stop rotation of the PTO output shaft.
The brake disc may be is splined to an output member of the clutch by lugs which engage circumferentially extending cut outs in the output member, the limited rotation of the PTO output shaft being limited by the circumferential extent of the cut outs.